Police exposed a seven-year-old boy to danger by helping move him and his mother out of Northern Ireland to be with her loyalist paramilitary agent partner, it has been claimed in the High Court.
A judge was told an Ulster Volunteer Force (UVF) unit was thought to be prepared to murder the woman's boyfriend if he could be located.
The terror grouping believed the suspected informer, who was on a witness protection programme, had betrayed them by collaborating with the authorities, according to a senior detective's assessment.
Details were disclosed as the child's father launched an action against the PSNI for alleged negligence and breach of the right to family life.
The man, who cannot be named to protect his child's identity, sued after tracking the boy down and winning a court order to have him returned home.
He claims his ex-wife left to go to England in March 2007, taking their son with her for what he was told was just a holiday.
His QC, Brian Kennedy, said police should have checked they were not breaching any duty of care before being involved in providing transport and accommodation for the mother and child.
Mr Kennedy claimed the operation involved an “elaborate system” of driving to various locations such as hotels and caravans.
To back his argument that the move jeopardised the child's safety, the barrister referred to the affidavit of a senior detective who monitored terrorist activity in the Ballymena area.
The court heard how UVF members in the area were assessed as attempting to identify any police officers who may have been in contact with the woman's new partner.
If they could locate the alleged informer himself he would be at risk of being murdered, according to the detective.
His view was that paramilitaries were prepared to go to “great lengths” to take revenge for his perceived betrayal.
“All this shows that this was a very serious scenario ... and (the boy's father) was never even notified about his son leaving the jurisdiction at all other than to hear from his wife that he was being taken on a two-week holiday,” Mr Kennedy said.
Asked by the judge, Mr Justice Gillen, whether he believed police should have blocked the move due to the threat against the suspected agent, the barrister replied: “They should have taken very careful steps before they lifted this boy from this jurisdiction with his mother, or allowed it to happen or were complicit in it happening without discussions with (the father).”
The hearing, expected to last for up to four days, continues.